The present invention generally relates to fuel-fired heating appliances and, in a preferred embodiment thereof, more particularly relates to a fuel-fired furnace having incorporated therein a specially designed draft inducer fan cooled during operation thereof by combustion air being flowed to the burner portion of the furnace.
Various types and sizes of fuel-fired air heating appliances are provided with draft inducer fans which are communicated with the interior of the heat exchanger portion of the appliance and serve to forcibly expel combustion gases therefrom and deliver the expelled combustion gases to a vent stack structure operatively coupled to the appliance. For example, in conventional forced draft, fuel-fired air heating furnaces the draft inducer fan is often located within the burner vestibule area of the furnace, with the negative pressure created in the vestibule area by the inducer fan being utilized to draw combustion air into the vestibule, via louvers or other openings in a wall portion of the vestibule, for delivery to the burners in the vestibule.
This conventional forced draft furnace construction carries with it several well known problems, limitations and disadvantages. For example, the essentially uncontrolled entry of combustion air into the burner vestibule area can undesirably cause flickering of the burner flames. Additionally, it is often the case that an undesirable level of burner and inducer fan operational noise is transmitted to areas near the furnace via the necessary louvers or other openings in the vestibule outer wall structure. Further, because the inducer fan is located in the enclosed vestibule area its motor can often be subjected to undesirably high operating temperatures.
AS can be seen from the foregoing, a need exists, in fuel-fired, forced draft furnaces and other types of fuel-fired, forced draft heating appliances, for an improved draft inducer design and use which eliminates or at least substantially reduces the above-mentioned problems, limitations and disadvantages. It is to this need that the present invention is directed.
In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, a fuel-fired, forced draft heating appliance, representatively an air heating furnace, is provided and has a chamber having an exterior wall with an air intake opening therein, a heat exchanger, and a fuel burner disposed in the chamber and operative to create hot combustion products in the heat exchanger.
A draft inducer fan is disposed in the chamber, has a motor, and is operative to forcibly expel flue gas from the heat exchanger. An air transfer housing structure extends through a portion of the chamber and is interconnected between the air intake opening and the motor. During operation of the furnace, the draft inducer fan creates within the chamber a negative pressure that draws combustion air into the chamber, for delivery to the fuel burner, sequentially through the air intake opening, through the interior of the air transfer housing structure, and against the motor in a manner cooling the motor and being preheated by the motor prior to delivery to the fuel burner within the chamber.
This use of the specially designed draft inducer fan apparatus with its air transfer housing portion substantially reduces burner and inducer fan noise escaping from the chamber, lowers the operating temperature of the inducer fan motor, and improves combustion efficiency via the preheating of the incoming combustion air.
According to another feature of the invention, an auxiliary fan blade structure is anchored to the inducer fan motor drive shaft for rotation therewith and, like the fan motor, is at least partially disposed within the interior of the air transfer housing. During furnace operation, driven rotation of this auxiliary fan blade structure serves to turbulate the combustion air interiorly traversing the air transfer housing structure and thereby facilitate heat exchange contact between the incoming combustion air and the inducer fan motor.
According to a further aspect of the invention, a baffle member is disposed within the chamber and is operative to inhibit flicker-creating impingement against the burner flame by the incoming combustion air exiting the air transfer housing structure. Representatively, the baffle member is a baffle plate secured to a support frame portion of the overall burner structure, and is interposed between the fuel burner and the outlet opening of the air transfer housing structure.
While principles of the invention are representatively illustrated and described herein as being incorporated in a fuel-fired, forced draft air heating furnace, it will be readily appreciated by those of ordinary skill in this particular art that such principles could also be advantageously utilized in a variety of other types of fuel-fired, forced draft heating appliances as well, and are not limited to being applied to furnaces.